The Deficit Reduction Act of 2005 (DRA) reauthorized the Temporary Assistance for Needy Families (TANF) block grant and made modifications expected to strengthen work requirements for families receiving cash assistance through state TANF programs. Both the U.S. Department of Health and Human Services (HHS) and states were required to take steps to implement these changes. Work participation rates, or the proportion of families receiving TANF cash assistance that participated in work activities, are the key performance measure HHS uses to assess state TANF programs. In response to the economic recession that began in 2007, the American Recovery and Reinvestment Act of 2009 (Recovery Act), provided additional TANF funding to eligible states and made additional modifications to TANF. GAO examined (1) How did DRA affect state TANF programs, including work participation rates? (2) How has the recent economic recession affected state TANF programs? (3) How did the Recovery Act affect state TANF programs? To address these questions, GAO analyzed federal TANF data, as well as relevant federal laws, regulations, and guidance; interviewed HHS officials; surveyed all state TANF administrators; and conducted site visits to meet with state and local officials in Florida, Ohio, and Oregon. GAO is not making recommendations in this report. Appended are: (1) Objectives, Scope, and Methodology; (2) Numbers of TANF Families Meeting Work Requirements in Recent Years; (3) Factors Affecting States' Ability to Meet Work Participation Rates; (4) Comments from the Department of Health and Human Services; and (5) GAO Contact and Staff Acknowledgments. (Contains 5 tables, 13, figures, and 67 footnotes.)